diff --git a/api/src/opentrons/protocol_engine/state/frustum_helpers.py b/api/src/opentrons/protocol_engine/state/frustum_helpers.py
index 95753e4f4e7d..604db4bfcf56 100644
--- a/api/src/opentrons/protocol_engine/state/frustum_helpers.py
+++ b/api/src/opentrons/protocol_engine/state/frustum_helpers.py
@@ -230,39 +230,39 @@ def get_well_volumetric_capacity(
 
     for segment in sorted_well:
         section_volume: Optional[float] = None
-        if segment.shape == "spherical":
+        if segment["shape"] == "spherical":
             if sorted_well[0] != segment:
                 raise InvalidWellDefinitionError(
                     "spherical segment must only be at the bottom of a well."
                 )
-                target_height=segment.topHeight,
-                radius_of_curvature=segment.radiusOfCurvature,
             section_volume = _volume_from_height_spherical(
+                target_height=segment["topHeight"],
+                radius_of_curvature=segment["radiusOfCurvature"],
             )
-        elif segment.shape == "rectangular":
-            section_height = segment.topHeight - segment.bottomHeight
+        elif segment["shape"] == "rectangular":
+            section_height = segment["topHeight"] - segment["bottomHeight"]
             section_volume = _volume_from_height_rectangular(
                 target_height=section_height,
-                bottom_length=segment.bottomYDimension,
-                bottom_width=segment.bottomXDimension,
-                top_length=segment.topYDimension,
-                top_width=segment.topXDimension,
+                bottom_length=segment["bottomYDimension"],
+                bottom_width=segment["bottomXDimension"],
+                top_length=segment["topYDimension"],
+                top_width=segment["topXDimension"],
                 total_frustum_height=section_height,
             )
-        elif segment.shape == "circular":
-            section_height = segment.topHeight - segment.bottomHeight
+        elif segment["shape"] == "circular":
+            section_height = segment["topHeight"] - segment["bottomHeight"]
             section_volume = _volume_from_height_circular(
                 target_height=section_height,
                 total_frustum_height=section_height,
-                bottom_radius=(segment.bottomDiameter / 2),
-                top_radius=(segment.topDiameter / 2),
+                bottom_radius=(segment["bottomDiameter"] / 2),
+                top_radius=(segment["topDiameter"] / 2),
             )
         # TODO: implement volume calculations for truncated circular and rounded rectangular segments
         if not section_volume:
             raise NotImplementedError(
-                f"volume calculation for shape: {segment.shape} not yet implemented."
+                f"volume calculation for shape: {segment['shape']} not yet implemented."
             )
-        well_volume.append((segment.topHeight, section_volume))
+        well_volume.append((segment["topHeight"], section_volume))
     return well_volume
 
 
diff --git a/api/tests/opentrons/protocols/geometry/test_frustum_helpers.py b/api/tests/opentrons/protocols/geometry/test_frustum_helpers.py
index 98a5f4e91008..48763fa9975c 100644
--- a/api/tests/opentrons/protocols/geometry/test_frustum_helpers.py
+++ b/api/tests/opentrons/protocols/geometry/test_frustum_helpers.py
@@ -53,7 +53,12 @@ def fake_frusta() -> List[List[Any]]:
                 topHeight=1.0,
                 bottomHeight=1.0,
             ),
-            SphericalSegment(shape="spherical", radiusOfCurvature=4.0, topHeight=1.0),
+            SphericalSegment(
+                shape="spherical",
+                radiusOfCurvature=4.0,
+                topHeight=1.0,
+                bottomHeight=0.0,
+            ),
         ]
     )
     frusta.append(
@@ -112,11 +117,23 @@ def fake_frusta() -> List[List[Any]]:
                 topHeight=3.0,
                 bottomHeight=2.0,
             ),
-            SphericalSegment(shape="spherical", radiusOfCurvature=3.5, topHeight=2.0),
+            SphericalSegment(
+                shape="spherical",
+                radiusOfCurvature=3.5,
+                topHeight=2.0,
+                bottomHeight=0.0,
+            ),
         ]
     )
     frusta.append(
-        [SphericalSegment(shape="spherical", radiusOfCurvature=4.0, topHeight=3.0)]
+        [
+            SphericalSegment(
+                shape="spherical",
+                radiusOfCurvature=4.0,
+                topHeight=3.0,
+                bottomHeight=0.0,
+            )
+        ]
     )
     frusta.append(
         [
@@ -129,7 +146,12 @@ def fake_frusta() -> List[List[Any]]:
                 topHeight=3.5,
                 bottomHeight=1.5,
             ),
-            SphericalSegment(shape="spherical", radiusOfCurvature=4.0, topHeight=1.5),
+            SphericalSegment(
+                shape="spherical",
+                radiusOfCurvature=4.0,
+                topHeight=1.5,
+                bottomHeight=0.0,
+            ),
         ]
     )
     return frusta
diff --git a/shared-data/python/opentrons_shared_data/labware/types.py b/shared-data/python/opentrons_shared_data/labware/types.py
index a491b67bbc94..d975640cc98e 100644
--- a/shared-data/python/opentrons_shared_data/labware/types.py
+++ b/shared-data/python/opentrons_shared_data/labware/types.py
@@ -126,6 +126,7 @@ class SphericalSegment(TypedDict):
     shape: Spherical
     radiusOfCurvature: float
     topHeight: float
+    bottomHeight: Literal[0.0] = 0.0
 
 
 class CircularFrustum(TypedDict):